We introduce perturbation and coupled-cluster theories based on a cluster mean-field reference for describing the ground state of strongly correlated spin systems. In cluster mean-field, the ground state wave function is written as a simple tensor product of optimized cluster states. The cluster language and the mean-field nature of the ansatz allow for a straightforward improvement which uses perturbation theory and coupled-cluster to account for intercluster correlations. We present benchmark calculations on the 1D chain and 2D square J 1–J 2 Heisenberg model, using cluster mean-field, perturbation theory, and coupled-cluster. We also present an extrapolation scheme that allows us to compute thermodynamic limit energies accurately. Our results indicate that, with sufficiently large clusters, the correlated methods (cPT2, cPT4, and cCCSD) can provide a relatively accurate description of the Heisenberg model in the regimes considered, which suggests that the methods presented can be used for other strongly correlated systems. Some ways to improve upon the methods presented in this work are discussed.

Abstract. Popsicle stick bombs are easy-to-build wooden constructions that probably reminisce a few funny moments of our childhood. In this work we look deeper in the travelling wave and we examine which parameters affect the height of the wave and how. We investigate the physics of bent materials and derive their potential energy around which we base our theoretical model. We present the results of the experiments that we performed which referred to the Young's modulus, the geometry of the sticks and their maximum height of the jump after the 'explosion'. We compare the experimental results with the theoretical predictions and we discuss these comparisons. Lastly, we propose potential improvements that might increase the precision of our model.